Image transfer process

ABSTRACT

A method of removing background image material from an image bearing substrate by means of coulombic attraction and the rearrangement of electrical charges.

United States Patent [191 Menz [451 July 17, 1973 52 Us; Cl. 96/1.4, 96/1 R [511 Int. Cl. G03g 13/22, 003 17/00 [58] Field of Search 96/1, 13, 1.4

[56] References Cited UNITED STATES PATENTS 3,384,565 5/1968 'liulaginet al 204/181 3,556,783 l/l970 Kyniakokis 96/1 .2

Primary Examiner-Charles E. Van Horn Attorney-James J. Ralabate, Raymond C. Loyer and David C. Petre [57] ABSTRACT h A method of removing background image material from an'image bearing substrate by means of coulombic attraction and the rearrangement of electrical charges.

, 23 Claims, 6 Drawing Figures IMAGE TRANSFER PROCESS BACKGROUND OF THE INVENTION The present invention relates in general to the transfer of images from an image bearing substrate to an image receiving surface and more particularly to the method of removing unwanted background image material from an image bearing substrate without transferring the desired image.

Various imaging processes are known wherein a thin film of material is deposited on a substrate or image bearing surface to provide a contrast to said surfacein image configuration. Due to the process steps employed, materials employed and defects therein, there is sometimes formed on the image bearing substrate unwanted imaging material in non-image or background areas of the image bearing substrate. Such unwanted image material is typically termed background material and is desirably eliminated by the use of optimum conditions and materials but many times even though such optimum conditions and materials are employed background material is found on the image bearing substrate after image formation.

One such imaging process which provides images comprising a thin film or layer of an insulating or semiconductive material on a substrate is the manifold imaging process as described in copending application Ser. No. 708,380, filed Feb. 26, 1968. In this imaging system, an imaging layer is prepared by coating a layer of electrically photosensitive imaging material onto a substrate. In one form the imaging layer comprises a photosensitive material such as metal-free phthalocyanine dispersed in a cohesively weak insulating or semi conductive binder. This coated substrate is called a donor. When needed the imaging layer is rendered cohesively weak. The process step of weakening the imaging layer is termed activation and in most cases the imaging layer is activated by contacting it with a swelling agent, solvent or partial solvent for the imaging layer. A receiver sheet is laid over the surface of the imaging layer and electric field is applied across the imaging layer while it is exposed to a pattern of light and shadow representative of the image to hereproduced. Upon separation of the donor substrate or receiver sheet, the imaging layer fractures along the lines defined by the pattern of light and shadow to which the imaging layer has been exposed. Part of the imaging layer is transferred to one of the sheets while the remainder is retained on the other sheet so that a positive image, that is, a duplicate of the original is produced on one sheet while a negative image is produced on the other.

As mentioned above due to imperfections in materials or image conditions, there is sometimes adhering to the donor and receiver sheets portions of the imaging layer which are not part of the image and are in the background areas. Such materials are unwanted as they detract from the appearance and usefulness of the image thus produced. In order to reduce the amount of background material on the images, optimum imaging materials and conditions are strived for and in some instances the process must be operated within narrow limits of the variables of the process. There is, therefore, stated a simple and efficient means of removing image background material so that the imaging processes which produce the image can operate with a broader range of variables and still produce pleasant appearing and useful images.

SUMMARY OF THE INVENTION It is, accordingly, an object of this invention to provide a'method of removing background material from an image bearing substrate to another substrate quickly and efficiently.

Another object of this invention is to provide a method of producing background-free images by means of the manifold imaging process.

Another object of this invention is to provide a two step image transfer process wherein an, image is transferred to an image receiving medium free of unwanted background material.

Another object of this invention is to provide an image transfer process wherein either the negative or positive image produced by the manifold imaging process is transferred to an image receiving medium free of unwanted background material.

These and other objects of this invention are apparent from the following description of the invention.

In accordance with this invention, there is provided a process whereby at least one of a releasable image and releasable image background material residing on an image bearing medium, provided by the manifold imaging process, is transferred to a receiving medium. The manifold imaging process provides images on various substrates which images retain a static electric charge due to the electric fields in which the electrically photosensitive imaging material is placed during said process. The independent transfer of either background material or manifold image is accomplished in accordance with this invention by sandwiching the image and background material between the image bearing medium and the receiving medium thus forming a transfer set. An electric field is then established across the image and background material and the image receiving medium which field can be supplied by a static charge in an insulating layer or applied from an external power source. When the polarity and potential of the electric field across the image material and background material are adjusted properly, one of the image or background material adheres to the receiving medium. Upon separation of the sandwich or set, there is provided a high quality image on one of the image bearing substrate or receiving medium while the background material is located on theother of the image bearing substrate and receiving medium.

The images produced by the manifold imaging process retain a static electric charge for a time after their production and such charge varies depending upon whether the electrically photosensitive material in the imaging layer of the manifold sandwich has been exposed to electromagnetic radiation to which it is sensitive or not so exposed. It has also been discovered that the difference in the amount of charge retention can be utilized to selectively remove the exposed imaging material whether in the form of an image or undesired background material from a substrate. In accordance with the process of this invention, for example, exposed background image material, can be selectively removed from a substrate leaving a clean backgroundfree positive image on said substrate. Alternatively, exposed negative images residing on a substrate together with non-exposed background material can be removed from that substrate to a receiving medium in accordance with the process of this invention leaving the background material on the substrate. Of course, positive and negative refers to the photographic sense of the image produced and, as is well known in the manifold imaging art, positive and negative images are not necessarily non-exposed and exposed portions of the imaging layer. Regardless of the image sense, the critical distinction is the exposure of the imaging material to electromagnetic radiation to which it is sensitive in the manifold imaging method.

Briefly, the process of this invention comprises transferring to a receiving medium exposed electrically photosensitive imaging materials from a substrate supporting both exposed and unexposed electrically photosensitive imaging material resulting from the manifold imaging process while said exposed and unexposed imaging materials retain their respective static electrical charges resulting from the manifold imaging process. The manifold imaging process is disclosed in copending applications Ser. No. 708,380, filed Feb. 26, 1968, Ser. No. 798,094, now abandoned, filed Feb. 10, 1969, Ser. No. 790,730, filed Jan. 13, 1969 and Ser. No. 803,386, now U.S. Pat. No. 3,615,393 filed Feb. 28, 1969, all of which are hereby incorporated by reference. Images produced by any of the processes described in said copending applications are referred to herein as manifold images. The process comprises sandwiching the imaging materials thus produced by the manifold imaging process between the image bearing substrate and a receiving medium, establishing an electric potential across the thus formed transfer set of sufficient strength to cause the actinic light exposed imaging material to adhere to the receiving medium but insufficient in strength to cause adhesion of the unexposed image mathe type of pigment employed, the conductivity of the receiving medium and the total electrical resistance offered by the image bearing substrate and the image receiving medium. The potential strength is easily determined as if it is too great both the unexposed and exposed imaging material adheres to the image receiving medium while if too small a potential is employed the exposed imaging material will not adhere to the image receiving medium.

As is known in the manifold imaging art, both conductive and electrically insulating donor and receiver sheets are employed in the manifold imaging process.

It has been found especially convenient foruse in this process that the manifold image to be separated from background material be provided on electrically insulating substrates. Such substrates retain a static charge from the manifold imaging process as well as does the imaging material residing on the substrate and such static charges can be employed to extend an electric field across the transfer set by means of electrically interconnected-conductive layers placed on each side of the transfer set. I

The image material employed in the manifold imaging process practice are usually electrically photosensitive materials dispersed in electrically insulating materials. Such image material retains a static electrical charge for at least a short period of time sufficient to perform the process of this invention. Typical insulating materials are polyethylene, polypropylene, polyamides, polymethacrylates, polyacrylates, polyvinyl chlorides, polyvinyl acetates, polystyrene, polythioloxanes, chlorinated rubber, polyacrylonitrile, epoxies, phenolics, hydrocarbon resins and other natural resins such as rosin derivatives as well as mixtures and copolymers of the above materials. Particularly preferred images which can be separated from background material according to the process of this invention are those comprising insulating materials which retain a charge and which are or can be rendered releasable from their respective substrates. Such materials include ,microcrystalline waxes such as: Sunoco 1290, Sunoco 5825, Sunoco 985, all available from Sun Oil Co.; Paraflint RG, available from the Moore and Munger Company; paraffin waxes such as: Sunoco 5512, Sunoco 3425, available from Sun Oil Co.; Sohio Parowax, available from Standard Oil of Ohio; waxes made from hydrogenated oils such as: Capitol City 1380 wax, available from Capitol City Products, Co., Columbus, Ohio; Caster Wax 13-2790, available from Baker Caster Oil Co.; Vitikote L-340, availablefrom Duro Commodities; polyethylenes such as: Polyethylene DYJT, Polyethylene DYLT, Polyethylene DYDT, all available from Union Carbide Corp.; Marlex TR 822, Marlex 1478, available from Phillips Petroleum Co., Epolene C 13, Epolene C-l0, available from Eastman Chemical Products Co.; Polyethylene AC6, Polyethylene AC6l 2, Polyethylene AC324, available from Allied Chemicals; modified styrenes such as: Piccotex 75, Piccotex 100, Piccotex 120, available from Pennsylvania Industrial Chemical; Vinylacetate-ethylene copolymers such as: Elvax Resin 210, Elvax Resin 310, Elvax Resin 420, available from E. I. DuPont de Nemours & Co., Inc., Vistanex MH, Vistanex L- available from Enjay Chemical Co.; vinyl chloride-vinyl acetate copolymers such as: Vinylite VYLF, available from Union Carbide Corp.; styrene-vinyl toluene copolymers; polypropylenes; and mixtures thereof.

The substrates upon which image material and background material can reside and be utilized in the process of this invention should be electrically insulating. Such electrically insulating substrates as can be employed in the manifold imaging process as described in the above incorporated copending application Ser. No. 708,380 can be employed in the process of this invention.

Also, the static charge remaining in the image material residing on a substrate from which background material has been removed can be used to transfer the image to another receiving medium to provide background free images on a wide variety of substrates.

in accordance with the process of this invention, background free images can be transferred to a wide variety'of image receiving media by forming a second transfer set.' For example, images can be transferred to cloth, drafting film, vellum, ordinary paper, leather, thermoplastic materials, photographic film, metals such as iron, silver, aluminum, tin, etc. In addition, im ages can be transferred free of background material in accordance with the process of this invention to irregular surfaces which would be unusable in the process by which the original image is formed. That is, in one or more of the process steps by which the image is originally formed, smooth surfaces are required least incomplete processing occur on an irregular surface. However, as will be seen in the following Examples, many different types of surfaces may be employed as the image receiving medium in the process of this invention. in addition, highly useful image receiving media can be employed such as metal or plastic lithographic plates. Surprisingly, high quality prints can be prepared from lithographic plates made from images transferred free of background material in accordance with the process of this invention.

The processes employed to transfer background free images utilizing the static charges thereon are described in copending applications Ser. No. 886,838,

filed Dec. 22, 1969 and Ser. No. 887,805 now U.S. Pat. No. 3,658,519, filed Dec. 24, 1969, both of which are incorporated herein by reference. The process described therein can be improved by exposing the image to be transferred to electromagnetic radiation to which the imaging material is sensitive for a brief period prior to transfer. When so exposed, lower transfer field strengths can be employed. Thus, a wider range of receiving media can be employed while still utilizing the residual static electric charges in the image bearing substrate to supply the field across the second transfer set.

The transfer of images or background material in accordance with the process of this invention is aided in some instances by coating the receiving media with an insulating liquid which aids in achieving good contact and release of the material either image or background. which is to be transferred to the receiving medium. The substance so employed in termed an activator. Preferably, the activator should have a very high electrical resistivity so as to prevent electrical breakdown of the transfer set. Activators usually employed in the manifold imaging method are useful here. As in the manifold,

imaging method, it will be generally found to be desirable to purify' commercial grades of insulating liquids so as to remove impurities which might impart a higher level of electrical conductivity. This may be accomplished by running the fluids through a clay column or by employing any other suitable purification technique.

Generally speaking, the activator may consist of any suitable material having the aforementioned properties. For purposes of this specification and the appended claims, the term activator shall be understood to include not only materials which are conventionally termed solvents but also those which are partial solvents, swelling agents or softening agents for the imag ing material. The activator can be applied at any convenient point in the process prior to separation of the sandwich.

It is generally preferable that the activator have a relatively low boiling point so that fixing of the image on the image receiving medium can be accomplished upon evaporation of the activator. Of course, if only background material is transferred, fixing is not a consideration. It is desirable that fixing of the image be accomplished quickly with mild heating at most. It is to be understood, however, that the invention is not limited to the use of these relatively volatile activators. in fact, very high boiling point non-volatile activators including silicone oils such as dimethyl-polysiloxanes and very high boiling point long chain aliphatic hydrocarbon oils ordinarily used as transformer oils such as Wemco-C transformer oil, available from Westinghouse Electric Co., have also been successfully utilized in the imaging process. Although these less volatile activators do not dry off by evaporation, image fixing can be accomplished by contacting the image with an absorbent sheet such as paper which absorbs the activator fluid.

In short, any suitable volatile or non-volatile activator may be employed. Typical activators include Sohio Odorless Solvent 3440, an aliphatic (kerosene) hydrocarbon fraction, available from Standard Oil Co. of Ohio, carbon tetrachloride, petroleum ether, Freon 214 (tetrafluorotetrachloropropane), other halogenated perchloroethylene, trichloromonofluoromethane, trichlorotrifluoroethane, trichlorotrifluoroethane, ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran, ethyleneglycol monoethyl ether, aromatic and aliphatic hydrocarbons such as benzene, toluene, xylene, hexane, cyclohexane, gasoline, mineral spirits and white mineral oil, vegetable oils such as coconut oil, babussu oil, palm oil, olive oil, castor oil, peanut oil and neatsfoot oil, decane, do-

decane and mixtures thereof. Sohio Odorless Solvent enough to transfer the light struck image material whether it be background material or image material while not great enough to transfer the nonexposed image material. For example, a negative image from the manifold imaging process is transferred in a field too weak to remove the background material which has not been exposed to actinic electromagnetic radiation. Basically, there are three modes by which the electrical field can be applied across the transfer set. The first is one in which the static electric charges retained by an insulating substrate from the manifold imaging process,

'the second is a separate electrically insulating sheet which can be inserted into the transfer set and the third is an applied electrical potential from a power source employing appropriate electrodes on each side of the transfer set.

In the first instance wherein the static electrical charges retained from the manifold imaging process are to be utilized the electric fields are established across the transfer set by backing the receiving medium with an electrically conductive layer and 1 connecting the conductive layer to a similar conductive layer contacting the electrically charged insulating image substrate. The two conductive layers are electrically interconnected; and, while so connected, the transfer set is separated. As is known to those skilled in the art, the strength of an electric field is lowered by separating the points of potential difference and the greater the distance, the lower the field strength. Thus, the potential supplied by the static charge retained by the image bearing substrate is employed to create fields of varying strengths by varying the total thickness of the transfer set bounded by the electrically interconnected conductive layers.

In the second instance, a separate dielectric electrically charged layer is employed as a backing on one of the image bearing substrate or the receiving medium. By properly placing the charged layer, with respect to polarity, conductive layers are then employed and electrically interconnected as described above in the form of backing members on each side of the transfer set. As above, the sandwich is then separated while the conductive layers are electrically interconnected. Also, as above, the strength of the electric field can be regulated not only by the amount of electrostatic charge in the charged layer but also by the distance between the points of potential difference. This distance is easily controlled by selecting the correct thickness of the receiving medium in the transfer set as well as its insulating property as will be more fully described below.

In the third instance, an applied electric field from an electrical power source can be utilized by placing the proper polarity across the transfer set by means of conductive electrodes which form a backing member for each of the receiving medium and the image bearing substrate. By properly adjusting the potential across the transfer set, only the light struck image material or background material will be transferred to the receiving medium. Other configurations will occur to those skilled in the art. 7

Static charges can be imposed upon dielectric layers by means known to the art or by contacting the layer with electrically charged electrode. Alternatively, the layer may be charged using corona discharge devices such as those described in US. Pat. No. 2,588,699 to Carlson, US. Pat. No. 2,777,957 to Walkup, US. Pat. No. 2,885,556 to Gundlach or by using conductive rollers as described in U. S. Pat. No. 2,985,834. Frictional means as described in U. S. Pat. No. 2,297,691 to Carlson or suitable apparatus can also be employed.

In all of the above described means by which selective transfer is achieved in accordance with the process of this invention, the amount of potential across the transfer set will be substantially below the calculated transfer voltage for transferring the non-exposed image material or non-exposed background material in the manifold imaging process. The general minimum transfer voltage for such non-light struck material is calculated according to the formula:

V nil im/ 1. R/Knn where V a constant for the image material K dielectric constant of the image material K, dielectric constant of the insulating image receiving medium D thickness of insulating image receiving medium D thickness of insulating image material In a case wherein the insulating image receiving medium is 1 mil in thickness and has a dielectric constant of 3.25, and the image material thickness is 0.2 mil having adielectric constant of 5, the calculated minimum transfer voltage for the non-light struck material is two thousand volts where the image material constant is 240 .and the image receiving medium is also the charged insulating layer. The transfer voltage for selectively transferring only the light struck material is substantially below two thousand volts.

The process of this invention includes the transfer of non-exposed image material from the image bearing substrate subsequent to the removal therefrom of exposed background material. That is, after removing the exposed background material by the process of this invention, a second transfer set is constructed by contacting the image with a receiving medium and placing an electric field across the image of the correct polarity and sufficient strength to transfer the image to the receiving media. Even when utilizing the residual static charges in the image material and image bearing substrate, the image can be transferred after removal of the background. When utilizing such residual static charges, transferrability is aided by exposing the previously non-exposed image material to actinic electromagnetic radiation prior to contacting it with a receiving medium in the second transfer set. Exposure to normal room light of about 2 to 3 seconds duration is sufficient to aid final transfer. The amount of exposure varies with the sensitivity of the electrically photosensitive material in the image material being transferred.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this novel method of separating selectively image material or background material will become apparent upon consideration of the detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:

FIG. la illustrates an image transfer set prior to communicating an electric field across the transfer set which field is supplied by the static charges in an insulating image bearing medium. The background material is exposed in the manifold imaging method which produced the image while the image is unexposed.

FIG. lb illustrates the transfer set of FIG. la after communication of an electric field across the transfer set showing transfer of the exposed background material.

FIG. 10 illustrates an image transfer set prior to communicating an electric field across the imaging material which field is supplied by static charges in an insulating image bearing substrate.

FIG. ld illustrates the image transfer set of FIG. la after the communication of an electric field across the set and separation of the set resulting in the transfer of the image material.

FIG. 2a illustrates another image transfer set wherein an electric potential is applied across the transfer set by means of a separate electrical power source.

FIG. 2b illustrates the transfer set of FIG. 20 after the application of an electric potential and the partial separation of the transfer set indicating transfer of background material.-

DETAILED DESCRIPTION OF DRAWINGS While FIGS. la-ld are expanded in order to facilitate the explanation of the process of this invention, it is to be understood that in actual operation the elements of the image transfer set are in contact with each other in the order shown in FIGS. Ia-ld.

In FIG. In there is provided releasable image material 2 sandwiched between electrically insulating image bearing medium 4 and electrically insulating receiving medium 6. Also residing on image bearing medium 4, is undesired background material 5. The transfer set resides between conductive layers 8 and 10. The image residing on image bearing medium 4 is provided by means of the manifold imaging process and image material 2 and background material 5 retain their static electric charges acquired in the process of producing the image. In FIG. la, a positive image is illustrated as image material 2 which represents the non-light struck or unexposed portions of the imaging layer employed in the manifold imaging process. Background material 5 represents light struck or exposed imaging material undesirably residing on a common substrate together with the image. Receiving medium 6 being electrically insulating is selected so as to have a thickness which reduces the strength of the electric field across the image material to the extent such that the non-light struck image will not transfer while the light struck background material will adhere to receiving medium 6. Referring now to FIG. lb, when image transfer is desired, an electrical connection is made between conductive layer 8 and conductive layer 10 by means of conductive wire 12 through switch 14. FIG. 1b illustrates background material 5 adhering to receiving medium 6 leaving image material 2 still adhering to image bearing medium 4. The electric potential across the transfer set is provided by the static charges retained in the electrically insulating image bearing medium which charges are acquired during the manifold imaging process which produced image.

FIGS. 1c and 1d illustrate another embodiment of this invention wherein background material and image material reside on a common substrate as in FIG. 1a. However, in FIG. 10 the negative image is shown as image material 2 meaning the light struck portions of the manifold imaging layer while background material 5 represents unexposed or non-light struck portions of the manifold imaging layer. With the exception of the exposed and unexposed imaging material, the reference number of FIGS. 1c and Id are as stated above for FIGS. la and 1b. The operative steps of the process are identical but as is indicated by FIG. 1d the light struck image transfers to receiving medium 6 and background material 5 remains on substrate 4.

FIGS. 2a and 2b illustrate another embodiment of the transfer process of this invention wherein the background material is transferred by means of applied electric field from an electrical power source adjusted properly to remove only the background material. Referring now to FIG. 2a, an expanded view, there is shown releasable image material 3] representing a positive image produced by means of the manifold imaging process and thus a non-exposed portion of the imaging layer together with image background material 32 which represents undesired light struck or exposed material adhering to image bearing medium 33. The image material is placed in contact with image receiving medium 35. The electric field is provided by a power source 36 through switching means 37 and electrodes 39 and 41. Referring now to FIG. 2b, when background removal is desired switch 37 is closed placing an electric potential across the transfer set. The potential is adjusted so as to cause the transfer of only the light struck background material leaving .the non-light struck or unexposed positive image residing on image bearing medium 33. Upon separation of the transfer set as shown in FIG. 2b, positive image material 31 remains residing on image bearing medium 33 while background material 32 adheres to receiving medium 35. In this embodiment, the electrical conductivity or insulating value of the respective image bearing substrate and the receiving medium are considered only when calculating the amount of potential to be placed across the transfer set.

The embodiments of this invention illustrated in FIGS. 1 and 2 above are representative of the various configurations of the background removal process of this invention. Such embodiments as illustrated may be performed manually or may be adapted for machine use. Those skilled in the art will appreciate that the process of this invention may be adapted for automatic and continuous modes of operation.

In addition, it has been discovered that subsequent to the transfer of unwanted background material from an image bearing substrate containing both background ferred to a different substrate than it was residing upon material and image material as described above, the image free of the background material, can be transwhen produced by means of the manifold imaging process. Such transfer process which can be carried out subsequent to removal of the background from the image bearing substrate are described in above mentioned copending applications Ser. Nos. 886,838 and 887,805. Accordingly, a three step process is provided herein whereby background free images on practically any type of substrate can be provided. The first step is the production of the image by means of the manifold imaging process as described in the above incorporated copending applications, the second step beingthe separation of the desired image from the unwanted background material produced by the manifold imaging process and the third step being the transfer of the clean image to a final desirable image substrate all of I which are accomplished by the processes disclosed herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following Examples further specifically illustrate the present invention. The Examples below are intended to illustrate various preferred embodiments of the transfer process of this invention. The parts and percentages are by weight unless otherwise indicated.

EXAMPLE I An imaging layer comprising electrically photosensi tive materials dispersed in a binder is first prepared. About parts of Naphthol Red B, code 207575 available from American Cyanamide Company is dissolved in reagent grade ethylenediamine. The solution is filtered immediately through coarse filter paper and the filtrate mixed with an equal volume of reagent grade isopropanol. The Naphthol Red B precipitates in the alcohol and is removed by means of a centrifuge. After separating the ethylenediamine and alcohol, the electrically photosensitive material is washed and filtered with successive amounts of isopropanol, a 2:1 volume mixture of isopropanol and deionized water and five washings with deionized water until the filtrate is neutral. Finally, the material is washed with dimethylformamide and methanol in succession until the filtrates have a pale yellow color. The Naphthol Red B is then dried at 40C under vacuum. About 3 parts of the purified Naphthol Red B is combined with about 45 parts of Naphtha and ball milled for 4 hours.

A binder material is prepared by combining about 2.5 parts of Paraflint RG, a low molecular weight parafinic material available from the Moore and Munger Co., New York City; about 3 parts of Polyethylene DYLT available from Union Carbide Corporation; about 0.5 parts of vinyl acetate-ethylene copolymer available as Elvax 420 from E. I. DuPont de Nemours Inc. and about 2.5 parts of a modified polystyrene on I mil Mylar with a No. 18 wire wound drawdown rod to provide a coating weight of 0.16 grams per square foot to produce a donor. The donor. is dried at a temperature of about 115F.

The donor is then placed on the tin oxide surface of a NESA glass plate with the imaging layer facing away from the tin oxide. The imaging layer is activated by ap plying Sohio Odorless Solvent 3440 by means of a brush and a sandwich is formed by placing a film of aluminized Mylar over the activated donor as a receiver. A black paper electrode is laid over the receiver sheet and a 5,000 volt d.c. potential is applied across the sandwich between the NESA glass plate and the black paper electrode. With the field applied, the imaging layer is exposed to a positive image by an incandescent white light source of 12.5 foot-candles for a period of 3 seconds through the transparent donor. With the potential still connected, the sandwich is separated yielding a pair of images with a positive image adhering to the donor sheet together with undesired background image material and a negative image on the receiver sheet. The positive image residing on the 1 mil Mylar base. is placed in contact with a 3 mil film of Mylar which film is residing on a conductive substrate. A conductive layer is placed over the 1 mil base and connected to the conductive substrate under the 3 mil Mylar film and with the two conductive layers connected the film and the base are separated revealing background material residing on the 3 mil Mylar film while the image remains on the l mil Mylar base free of background material. The 3 mil Mylar film containing the background material from the image is replaced with a paper litho master and the image residing on the 1 mil Mylar base is placed on the paper litho master. The conductive layers are again electrically interconnected and while so connected the litho master and 1 mil Mylar base are separated leaving the positive image residing on the litho master free of background material. The litho master is then employed in a conventional lithographic process utilizing olephilic ink while the paper is wetted with water to provide background free lithographic prints of the positive image.

EXAMPLE [I A black imaging layer useful in the manifold imaging process is prepared by combining about 5 grams of X- form phthalocyanine with about 5 grams Algol Yellow GC, l,2,5,6-di-(C)C '-diphenyl thiazole-anthraquinone, C.I. No. 67300, available from General Dyestuffs Corporation, and about 2.8 grams of purified Watchung Red B, 'l -(.4'-methyl-5-chloro-2'-sulfonic acid) azobenzene-2-hydroxy-3-naphthoic acid, C.l. No. 15865, available from E. l. DuPont de Nemours & Co., about 8 grams of Sunoco Microcrystalline Grade 5825 having an ASTM melting point of l5lF, available from Sun Oil Company and about 2 grams Paraflint RG, a low molecular weight paraffinic material available from the Moore and Munger Company, New York City and about 320 ml. of petroleum ether (90-l20C) and about 14 ml. of Sohio Odorless Solvent 3440 are placed with a mixed pigments in a glass jar containing 5: inch flint pebbles. The mixture is then milled by revolving the glass jar at about 70 r.p.m. for about l6 hours. The mixture is then heated for approximately 2 hours at about 45C and allowed to cool to room temperature. The paste-like mixture is then coated in subdued green light on a 1 mil thick Mylar sheet by means ofa No. 22

wire wound drawdown rod to produce a coating weight of about 0.27 grams per square foot. The thus formed donor is employed in the manifold imaging process with a conductive aluminum sheet as a receiver. The imaging layer is exposed to a positive image. The voltage applied during imaging and subsequent separation of the donor and receiver sheets is 4 KV/mil of insulating material. A positive image with background material is thus produced on the donor with residual voltage remaining on the image material and the donor sheet. Under safelight conditions, the image is contacted with a sheet of 3 mil thick Mylar receiving medium backed with a conductive metal layer to form a transfer set. A conductive rubber sheet is laid over the 1 mil donor and electrical contactis made between the conductive metal backing and the conductive rubber sheet. The donor together with the conductive rubber sheet is pulled from the receiving medium leaving the image residing on the donor and the background material residing on the receiving medium.

EXAMPLE [I] The method of Example I is repeated with the exception that the red imaging material is coated onto a 2 mil thick Mylar donor sheet instead of the l mil thick Mylar donor material employed in Example I. After separation of the manifold sandwich thereby producing a positive image on the donor sheet together with background material which was exposed to the actinic electromagnetic radiation a 6 mil thick Mylar sheet is laid over the image and background material. Conductive sheets are placed on each side of the transfer set, that is, adjacent the 2 mil Mylar donor sheet and adjacent the 6 mil Mylar receiving medium which conductive sheets are then electrically interconnected. Upon separation of he transfer set, there is revealed a background free image remaining on the donor sheet while the background formerly residing on the donor now resides on a 6 mil Mylar receiving medium.

EXAMPLE iv The background free image produced in accordance with the process of Example 1]] is exposed to room light of about foot-candles for about 2 seconds andis then contacted with a clean 6 mil thick receiver. The transfer set is then bounded on each side by conductive sheets as in the previous Example which conductive sheets are electrically interconnected. While the sheets are electrically interconnected, the transfer set is separated revealing the background free image residing on the 6 mil Mylar receiving medium while the 2 mil Mylar donor is substantially free of imaging material.

EXAMPLE V The procedure of Example I is repeated with the exception that the receiving medium is l mil Mylar and the transfer set is held together for about 5 seconds longer than in, Example I. Upon separation of the set, there is revealed a background free image residing on the receiver while background material resides on the 1 mil Mylar. This Example indicates that in the event the transfer set held together with the conductive layers electrically interconnected for a brief period of time subsequent to initial transfer, the background material transfers back to the image bearing substrate while the image transfers to the receiving medium under a field of sufficient strength.

Although specific components and proportions have been stated in the above description of preferred embodiments of the invention, other typical materials as listed above as suitable may be used with similar results. In addition, other materials may be added to the various components of the process to synergize, enhance or otherwise modify the properties of the imaging layer. For example, various dyes, spectral sensitizers, activators or electrical sensitizers such as Lewis acids may be added to the several components of the manifold sandwich. I

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

l. A method of selectively removing one of an electrically photosensitive visible manifold image pattern of material and electrically photosensitive background image material from a common image bearing substrate wherein one of said image and background material has been exposed to actinic electromagnetic radiation in the manifold imaging method said substrate being one of the donor and receiver sheets previously employed in the manifold imaging method whereby said image pattern is formed by exposing said material in an imaging layer to a pattern of actinic electromagnetic radiation and fracturing said layer upon separation of said sheets while under an electric field, said image and background materials retaining their respective residual electric charges from said method, which comprises forming a transfer set by contacting said image and background material with a receiving medium, subjecting said set to an electric field of sufficient strength to transfer to said receiving medium the exposed material, said strength being insufficient to transfer the unexposed material, and separating said transfer set.

2. The method of claim 1 wherein the image bearing substrate retains the static charges acquired in the manifold imaging method and said static charges are extended across the transfer set by electrically interconnecting conductive layers on each side of said set.

3. The method of claim 1 wherein the electric field is applied from an external power source.

4. The method of claim 1 wherein the image is exposed to actinic electromagnetic radiation in the manifold imaging method and said image transfers to said receiving medium.

5. The method of claim I wherein the electric field is applied by a separate electrostatically charged layer and said charges are employed to extend said field across said transfer set by electrically interconnecting conductive layers on each side of said set.

6. The method of claim 5 wherein the electrostatically charged layer is the receiving medium.

7. The method of claim I wherein the background material is exposed to actinic electromagnetic radiation in a manifold imaging method and said background transfers to said receiving medium.

8. The method of claim 7 wherein the electrically photosensitive material is an organic material.

9. The 'method of claim 7 wherein the receiving me- I a. providing an electrically photosensitive imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to actinic electromagnetic radiation, sandwiched between a donor sheet and a receiver sheet;

b. subjecting said imaging layer to an electric field and exposing said layer to a pattern of actinic electromagnetic radiation whereby some areas of said layer are exposed and other areas of said layer are non-exposed;-

. separating said donor and receiver sheets while under said field whereby said imaging layer fractures in imagewise configuration providing a negative image with background material on one of the donor and receiver sheets and a positive image with background material on the other sheet;

background material on at least one of said donor and receiver sheets with a receiving medium;

; subjecting said transfer set to an electric field of sufficient strength to transfer only exposed image material to said receiving medium; and.

f. separating said transfer set.

11 The method of claim 10 wherein the electrically photosensitive imaging layer comprises an organic electrically photosensitive material dispersed in an insulating binder.

12. The method of claim 11 wherein the imaging layer of step (a) is initially nonfracturable and further including the step of rendering said electrically photosensitive imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to actinic electromagnetic radiation by contacting said imaging layer with an activating amount of an activator.

13. The method of claim 11 further including the step of exposing the image to actinic electromagnetic radiation subsequent to separating the transfer set and forming a second transfer set by contacting said image with a receiving medium, subjecting said second transfer set to an electric field of sufficient strength to transfer said image to said receiving medium and separating said second transfer set.

14. The method of claim 1 1 wherein said transfer medium is coated with an activator fluid upon contacting said image and background material whereby contact between said medium and material is improved and 'said material is released from said substrate.

15. The method of claim 11 wherein the donor sheet is electrically insulating and retains electrostatic charges after separation from the receiver sheet and the electric field across the transfer set is supplied by electrostatic charges in the receiving medium, by placing electrically interconnected conductive layers on each side of said transfer set.

16. The method of claim 15 wherein the background material on said donor has been exposed to actinic electromagnetic radiation and said background transfers to said receiving medium.

17. The method of claim l6 further including the step of exposing the image remaining on said donor to actinic electromagnetic radiation subsequent to the sepa ration of said transfer set, forming a second transfer set by contacting said image on said donor with a transfer medium, subjecting said transfer set to an electric field of sufficient strength to transfer said image to said receiving medium and separating said second transfer set.

. forming a transfer set by contacting the image and 18. The method of claim 11 wherein the receiver sheet is electrically insulating and retains electrostatic charges after separation from said donor sheet, and the electric field across said transfer set is provided by the electrostatic charges on said receiver by placing electrically interconnected conductive layers on each side of said transfer set.

19. The method of claim 18 wherein the image on said receiver sheet is exposed to actinic electromagnetic radiation in step (b) and said image transfers to said transfer medium leaving the background material on said receiver sheet.

20. A method of transferring an electrically photosensitive visible manifold image pattern of material, said material remaining unexposed to electromagnetic radiation to which it is sensitive, from a substrate, said substrate also supporting electrically photosensitive background image material which background material has been exposed to electromagnetic radiation to which it is sensitive, said materials comprising l-(2'- methoxy-S'-nitrophenylazo)-2-hydroxy-3"-nitro-3- napthanilide, said substrate being one of the donor and receiver sheets previously employed in the manifold imaging method whereby said image pattern is formed by exposing said materials in an imaging layer to a pattern of actinic electromagnetic radiation and fracturing said layer upon separation of said sheets while under an electric field and wherein said manifold image and background material retain their respective electrostatic charges from the manifold imaging method which comprises forming a transfer set by contacting said image and background material with a receiving medium, subjecting said transfer set to an electric field of sufficient strength to transfer said manifold image and background material to said receiving medium, maintaining said receiving medium in contact with said image and background material for about 5 seconds whereby said background material adheres to said substrate, and separating said transfer set whereupon said image pattern of material resides on said receiving medium and said background material adheres to said substrate.

21. The method of claim 20 wherein the substrate retains the static charges acquired in the manifold imaging method and said static charges are extended across the transfer set by electrically interconnecting conduc tive layers on each side of said set 22. The method of claim 20 wherein the electric field is applied from an external power source.

23. The method of claim 20 further including the step of exposing the image on said receiving medium to actinic electromagnetic radiation subsequent to the separation of said transfer set, forming a second transfer set by contacting said image on said receiving medium with a transfer medium, subjecting said second transfer set to an electric field of sufficient strength to transfer said image to said transfer medium and separating said second transfer set. 

2. The method of claim 1 wherein the image bearing substrate retains the static charges acquired in the manifold imaging method and said static charges are extended across the transfer set by electrically interconnecting conductive layers on each side of said set.
 3. The method of claim 1 wherein the electric field is applied from an external power source.
 4. The method of claim 1 wherein the image is exposed to actinic electromagnetic radiation in the manifold imaging method and said image transfers to said receiving medium.
 5. The method of claim 1 wherein the electric field is applied by a separate electrostatically charged layer and said charges are employed to extend said field across said transfer set by electrically interconnecting conductive layers on each side of said set.
 6. The method of claim 5 wherein the electrostatically charged layer is the receiving medium.
 7. The method of claim 1 wherein the background material is exposed to actinic electromagnetic radiation in a manifold imaging method and said background transfers to said receiving medium.
 8. The method of claim 7 wherein the electrically photosensitive material is an organic material.
 9. The method of claim 7 wherein the receiving medium is wetted with an activator fluid whereby contact with said material is improved and said material is released from said substrate.
 10. A process which comprises the steps of: a. providing an electrically photosensitive imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to actinic electromagnetic radiation, sandwiched between a donor sheet and a receiver sheet; b. subjecting said imaging layer to an electric field and exposing said layer to a pattern of actinic electromagnetic radiation whereby some areas of said layer are exposed and other areas of said layer are non-exposed; c. separating said donor and receiver sheets while under said field whereby said imaging layer fractures in imagewise configuration providing a negative image with background material on one of the donor and receiver sheets and a positive image with background material on the other sheet; d. forming a transfer set by contacting the image and background material on at least one of said donor and receiver sheets with a receiving medium; e. subjecting said transfer set to an electric field of sufficient strength to transfer only exposed image material to said receiving medium; and f. separating said transfer set.
 11. The method of claim 10 wherein the electrically photosensitive imaging layer comprises an organic electrically photosensitive material dispersed in an insulating binder.
 12. The method of claim 11 wherein the imaGing layer of step (a) is initially nonfracturable and further including the step of rendering said electrically photosensitive imaging layer structurally fracturable in response to the combined effects of an electric field and exposure to actinic electromagnetic radiation by contacting said imaging layer with an activating amount of an activator.
 13. The method of claim 11 further including the step of exposing the image to actinic electromagnetic radiation subsequent to separating the transfer set and forming a second transfer set by contacting said image with a receiving medium, subjecting said second transfer set to an electric field of sufficient strength to transfer said image to said receiving medium and separating said second transfer set.
 14. The method of claim 11 wherein said transfer medium is coated with an activator fluid upon contacting said image and background material whereby contact between said medium and material is improved and said material is released from said substrate.
 15. The method of claim 11 wherein the donor sheet is electrically insulating and retains electrostatic charges after separation from the receiver sheet and the electric field across the transfer set is supplied by electrostatic charges in the receiving medium, by placing electrically interconnected conductive layers on each side of said transfer set.
 16. The method of claim 15 wherein the background material on said donor has been exposed to actinic electromagnetic radiation and said background transfers to said receiving medium.
 17. The method of claim 16 further including the step of exposing the image remaining on said donor to actinic electromagnetic radiation subsequent to the separation of said transfer set, forming a second transfer set by contacting said image on said donor with a transfer medium, subjecting said transfer set to an electric field of sufficient strength to transfer said image to said receiving medium and separating said second transfer set.
 18. The method of claim 11 wherein the receiver sheet is electrically insulating and retains electrostatic charges after separation from said donor sheet, and the electric field across said transfer set is provided by the electrostatic charges on said receiver by placing electrically interconnected conductive layers on each side of said transfer set.
 19. The method of claim 18 wherein the image on said receiver sheet is exposed to actinic electromagnetic radiation in step (b) and said image transfers to said transfer medium leaving the background material on said receiver sheet.
 20. A method of transferring an electrically photosensitive visible manifold image pattern of material, said material remaining unexposed to electromagnetic radiation to which it is sensitive, from a substrate, said substrate also supporting electrically photosensitive background image material which background material has been exposed to electromagnetic radiation to which it is sensitive, said materials comprising 1-(2''-methoxy-5''-nitrophenylazo)-2-hydroxy-3''''-nitro-3-napthanilide, said substrate being one of the donor and receiver sheets previously employed in the manifold imaging method whereby said image pattern is formed by exposing said materials in an imaging layer to a pattern of actinic electromagnetic radiation and fracturing said layer upon separation of said sheets while under an electric field and wherein said manifold image and background material retain their respective electrostatic charges from the manifold imaging method which comprises forming a transfer set by contacting said image and background material with a receiving medium, subjecting said transfer set to an electric field of sufficient strength to transfer said manifold image and background material to said receiving medium, maintaining said receiving medium in contact with said image and background material for about 5 seconds whereby said background material adheres to said substrate, and separating said transfer set whereupon said image pattern of material resides on said receiving medium and said background material adheres to said substrate.
 21. The method of claim 20 wherein the substrate retains the static charges acquired in the manifold imaging method and said static charges are extended across the transfer set by electrically interconnecting conductive layers on each side of said set.
 22. The method of claim 20 wherein the electric field is applied from an external power source.
 23. The method of claim 20 further including the step of exposing the image on said receiving medium to actinic electromagnetic radiation subsequent to the separation of said transfer set, forming a second transfer set by contacting said image on said receiving medium with a transfer medium, subjecting said second transfer set to an electric field of sufficient strength to transfer said image to said transfer medium and separating said second transfer set. 